Carburetor for internal combustion engines



June 28, 1955 w. ZARNACK 2,711,384

CARBURETOR FOR INTERNAL COMBUSTION ENGINES Filed June 15, 1951 fm eman'WERNER zA/M Ac/ -8 ZVM United S ttes Fatent C F CARBURETOR FOR INTERNALCOMBUSTION ENGINES Werner Zarnack, Lockstcdter Lager-Noni, near Itzehoe,Germany Application June 15, 1951, Serial No. 231,685

Claims priority, application Germany June 20, 1950 2 Claims. (Cl.261-44) 1 This invention relates to carburettors for internal combustionengines.

Carburettors of this type are known where the mixture of air and fuel isproduced at the place of its highest flow velocity and the proportion ofthe mixture components is automatically adjusted by a controller inaccordance with a desirable scheme and independently upon the pressureat the mixture forming place.

With these carburettors the cross-section must be re duced at thethrottle place to a greater extent than in the air supply in order tocreate a decrease in pressure which sufiices for the control and theatomization of the fuel being sucked-in by a vacuum at the throttlingplace. If the device is partially loaded, for instance, if the throttleslide is partially closed, the flow velocity automatically increasesbetween the mixture forming place and the air measuring nozzle if thelatter is located before the throttling place. If the throttle slide isfully opened, however, and if the carburettor is not suflicientlyrestricted at the throttling place it may happen that the rate of thepressure decrease does not suflice for the regulation and atomization ofthe fuel. On the other hand, if the carburettor is throttledexcessively, this may cause a reduction of the fuel output.

If the pressure decrease at the mouth of the atomizing nozzle is notsufficient, the regulator passes into its fully open end position. Inthis case the amount of fuel depending on the added resistance from thefloat chamber to the mouth of the atomizing nozzle is too small. Thisparticularly happens if additional air is admixed to the fuel on its wayfrom the regulator to the nozzle to improve atomization because a smalladmixture of air already sufiices to considerably enlarge the resistanceat the mouth of the atomizing nozzle. Since, however, the air admixturecannot be dispensed with in view of the required atomization the crosssection at the mixture in accordance with a predetermined scheme,atomized air in supplied through an air slide coupled with the throttleslide of the carburettor as soon as with the partially closed throttleslide for the combustion air the pressure decrease at the atomizingnozzle has reached a value which allows the admixture of atomized airwithout in v fiuencing the control.

It has been found that it is preferable to stop the admission ofatomized air if between three quarters and full load is reached. Whenthe admission of atomized air is stopped the fine preparation of thefuel is only attained by the speed of the flow of the combustion airthrough the atomizing nozzle.

It was found that for the attainment of a minimum of fuel consumption itis highly important to have the atomization and the uniform mixture takeplace immeverted into pressure.

2,711,884 Patented June 28, 1955 diately at the mixing place. For thispurpose a cylindrical throttle slide of the type is applied as used inconnection with carburettors of motor cycles if the fuel is fedlaterally at the periphery of the smallest cross section. Generally, thecarburettors of motor cycles are provided in this case with acollar-like projection on the slide, said projection serving as make andbreak edge for the fuel escaping in the flow direction before the collarand being at this place mixed with air.

Excellent atomizing results are obtained in conformity with theinvention by the formation of the throttle edge in such a manner thatthe possibly reduced creation of little whirls takes place at thesmallest cross section of the feed pressure difference are possiblyconverted into flow velocity.

With this purpose in view the front face of the cylindrical slide isbevelled at the entrance edge nearly up to its center and is rounded. Ifthis slide is partially closed a Venturi-tube-like narrowing results.The exit opening for the fuel is surrounded by a narrow ledge only atthe front face of the cylindrical slide since the surface of the slideis preferably cut as an angle of 45 relative to the axis of the slide.In this manner a maximum of air flow at the mixture forming place anddue to the reduction of whirls an optimal pressure decrease results. Atthe same time a mixture forming chamber is created having sufficientspace for the entrance of the fuel and preventing final deposition atthe projecting surface. As the flow velocity of the fuel mixed with theatomized air at the exit is nearly as great as that of the combustionair flowing in preferably rectangular direction thereto, the flowdirection of the fuel jet will be inclined at an angle of about 45degrees.

Another feature of the invention relates to a method of preparing thefuel mixture where the fuel is fed along the axis of the air flow andstop of the atomized air flow, even if fully loaded, is presented theknown action of the multiplicator nozzle being utilized at the mixtureforming place. A small Venturi-tube is used for the formation andcontrol of the mixture in such a manner that the mouth of this smalltube having the spraying tube located in its smallest cross sectionopens into the smallest cross section of an outer air hopper feeding themain flow of the combustion air. In this manner the pressure decrease atthe mouth of the spraying tube is increased in proportion of the exitcross section of the I small Venturi-tube to its smallest cross sectionrelative to the use of only one sole air hopper, provided that theenlarging cone of the small Venturi-tube is so flat that the flowingvelocity in the enlargement is fully con- The enlargement of thepressure decrease is limited in the customary carburettors because inaccordance with a large pressure decrease the main nozzle isproportionally reduced to the multiplicator effect; in this mannerdimensions result which are so small that they interfere with theworking safety of the carburettor. Since in these carburettors themultiplicator tube is arranged in the flow direction before the throttlechamber also the produced mixture, when partially loaded, is depositedat the surface of the throttle device arranged across the flow directionand must be formed again at the edge of thte throttle fiap in the mannerof the carburettors not provided with multiplicator nozzles.

In conformity with a further feature of the invention the multiplicatortube of a carburettor having automatic fuel control is located in thevery throttle cross section and is so dimensioned that a greatestpossible multiplicator effect is obtained at the narrowest place of thesmall Venturi-tube. The vacuum produced at the narrowest place of themultiplicator tube may be five to six times as great as the flow vacuumat the narrowest place a of the carburettor; in this manner the rate ofpressure decrease sufiices for the regulation and it is possible to addatomized air from the running without load until the running with fullload without the regulator moving into its end position or the crosssection of the carburettor being inadmissibly restricted if running withfull load.

If the above described throttle slide is used the multiplicatoratomizing nozzle may be arranged in parallel to the main air flow of thecarburettor in such a manner that the conical enlargement preferablyopens rectangularly to the main fiow direction of the suction air of thecarburettor. This enlargement may also be arranged at the periphery ofthe throttle cross section and coaxially with the latter.

1 In conformity with a further feature of the invention the axis of themultiplicatornozzle is arranged coincidentally with the middle axis ofthe air flow so that a more uniform mixture is formed over the entirecross section. Due to the multiplicator effect the mixture of fuel andatomized air escapes into the main air flow of the multiplicator tubepractically with sound velocity from running empty up to running withfull load.

It is apparent from the above that the invention solves the problem ofproviding controlling means for a carburettor which automaticallyregulates the fuel mixture according to a desired order said controllingmeans enabling the production of a sufficient rate of pressure decreasetowards vacuum over the entire load range, but. not narrowing the crosssection of the suction tube to such an extent that this narrowing leadsto pressure losses. For this purpose the feeding of atomized air isstopped according to the invention within the range of about threequarters and full load and a. multiplicator atomizing nozzle is arrangedwithin the throttle cross section. The fact that it is already known perse to regulate the additional air in dependency upon the adjustment ofthe throttle flap, to use a Venturi-tube atomizer and to provide asymmetrically adjustable throttle having a changeable Venturi crosssection does not interfere with the novelty and usefulness of thecombination of means in accordance with the invention.

Several preferred embodiments of the invention are illustrated in theattached drawings.

In these drawings,

Fig. l is a vertical sectional View of a carburettor constructed inconformity with the invention,

Fig. 2 is a vertical sectional view of the throttle slide,

Fig. 3 is a front view of the slide shown in Figure 2,

Figs. 4 and 5 are vertical sectional views of a further embodiment ofthe invention. Figure 5 being a scctiona1 view on line 5 to 5 of Figure4.

In conformity with Fig. l the fuel is sucked in through spray nozzle 1by the vacuum prevailing in the part of the carburettor having thesmallest cross section. The output of the motor is limited by the slide2. The quantity of air sucked in is controlled at the constriction 3 ofthe air suction joint, said constriction being shaped in accordance withthe known rules to measure the rate and quantity of the air flow. Thesucked-in air controlled pressure volume is by the difference at theinlet openings of the pipes 4 and 5.

The fuel enters into the float chamber 7 through pipe 6 and flowsthrough pipe 8 to the main orifice 9. Posterior to this orifice 9 achannel 10 leads to the chamber 11 of the fuel regulator. In thisfuel-filled chamber the same vacuum prevails as posterior to the mainorifice 9. The chamber 12 of the fuel regulator is connected by pipe 5with the narrowest portion of the nozzle 3. Chambers 11 and 12 areseparated from each other by the membrane 13. The fuel supply iscontrolled by a valve of which the needle 14 coacts with a flat seatprovided at the exit of nozzle 15 and is adapted to fully close it.

If the sucked-in air volume increases by opening the throttle slide 2,the vacuum in the nozzle 3, the pipe 5 and the chamber 12 alsoincreases. The membrane 13 is moved to the left and clears the passagethrough the nozzle 15; thereby also the vacuum posterior to the fuelnozzle 9 increases. This vacuum tends to move the membrane again to theright, until the pressure within the chambers 11 and 12 is equalized.

In the embodiment of the invention shown in Fig. 1 the atomized air issucked-in through nozzle 19, which is controlled by a slide 16. Thisslide 16 is connected by rod 17 with the one arm of a double armed lever18; the other lever arm is connected with slide 2 by rod 171:. Lever 18is rotatably supported upon pivot 18a. If the throttle 2 has opened thecross section of the carburettor, e. g. for three quarters, the slide 16stops the entrance of the atomized air through nozzle 19. Thechange-over time may be altered in accordance with the Workingconditions of the carburettor by an adjusting device provided inconnection with rod 17, but not shown in the drawmgs.

The shape of the slide 2 is more clearly shown in Figs. 2 and 3.

As apparent from these figures numeral 20 denotes the throttling edge ofthe slide. The shape of the en trance edge 21 of the slide is apparentfrom Fig. 3, this edge 21 contrary to the customary shapes is bevelledand rounded in order to possibly eliminate loss of pressure of the airpassing the throttling edge or the mouth of the nozzle. The edge 21forms a straight intersecting line with the front face of the slide 2.The intersecting line is so far displaced beyond the middle of the slide2 that the discharge edge may embrace the nozzle mouth with an optuseangle a, as apparent from Fig. 3. Since the air is admixed to the fuelexiting from spraying nozzle 1 it is discharged from this nozzle withessentially the same speed as the combustion air flowing perpendicularlythereto. In order to prevent the fuel to meet baffle faces the slide 2is bevelled posterior to the edge forming the optuse angle at an angleof preferably 45. This bevelled face of the slide 2 is designated inFigs. 2 and 3 with the refer ence numeral 22.

In the embodiment of the invention shown in Figs. 4 and 5 the pipes 22'and 23 correspond to the pipes 5 and 4 of Fig. 1 respectively. Also thisconstriction 24 of the air suction pipe is constructed in accordancewith accepted rules.

The air nozzle 19 of Fig. 1 corresponds to the nozzle 25 of Fig. 5.

According to this embodiment of the invention the supply of atomized airis not controlled in dependency upon the throttle adjustment; in thiscase a vacuum increasing tube-shaped device is provided having its ontrance opening located along the center axis of the constriction 24 andits exit in the center axis of the narrowest throttle cross section. Asa result of the action and of the spraying nozzle 26 of this tube therate of pressure decrease at the mixing place 27 of the tube alwayssuffices to allow the admixture of atomized air by the nozzle 25 withinthe entire loading range of the motor. The spraying nozzle 26 evencauses that the vacuum at the two exit places reaches the critical rateof pressure decrease if the slide is partially closed whereby the airflows in this case through the nozzle 26 with the velocity of the sound.

The fuel pipe 28 shown in Fig. 5 corresponds to the fuel pipe 5 shown inFig. 1 leading from the controller to the spraying nozzle 1. Thespraying nozzle 26 may be arranged at one side within the air suctionpipe, but it is recommendable in view of a satisfactory air flow andobtainment of the vacuum if this mixing nozzle for the fuel and thecombustion air is provided in the middle axis of the air suction pipe.With this purpose in view, two slides 29, Figure 4, moving in oppositedirections are used for throttling the air of combustion, said slidesbeing actuated in the manner indicated in Figs. 4 and 5. In the casingof the air suction joint the axis 35 of a double-armed lever 30 ispivotally supported. T he main operating lever 31 of the carburettor isattached to the same axis 35. The two ends of the double-arm lever 30are pivotally connected by means of connecting rods 33 with the one endof two other double-arm levers 32 and 32a respectively, the other endsof which are connected with the slides 29 by pushing rods 34. If thedouble-arm lever 30 is rotated about its axis in the clockwise directionthe throttle slides are outwardly moved. If, however, the double-armlever turns in an anti-clockwise direction the throttle slides moveinwardly and stop the air supply. Instead of the throttle slidesflap-like controlling organs may be provided.

The entrance edges of the throttle slides or valves 29 are rounded in asimilar way as the entrance edge of throttle valve 2 shown in Fig. 3;however, the slides are each provided with a semi-cylindrical recess 35adapted to enclose the opening of the spray nozzle 26, if the slides 29are in their idle position. The discharge edges of the throttle slidesare enlarged into flat portions so that in the fully opened positionshown in Fig. 4 they will reduce without causing throttling losses theflow velocity of the air from the narrowest place up to the place atwhich the slides 29 have the largest distance from each other. In thismanner the fiow resistance of the carburettor has in the fully openedposition of the slides 29 the smallest possible output so that the motorwill have its maximum efficiency, if the slides 29 are fully opened. Bynarrowing the cross section at the slides 29 to their fully openedposition a vacuum is produced at the mouth of the spraying nozzle 26,which vacuum suffices for the continuous .5

supply of atomized air through the nozzle 25.

Having thus particularly described the nature of my said invention andthe manner in what the same is to be performed, What I wish to havecovered by Letters Patent is:

1. Carburettor for internal combustion engines cornprising, incombination, an air pipe having a venturi adapted to form the mixtureand to produce a vacuum for sucking-in the fuel, a spraying nozzleprovided at the venturi of said air pipe, a regulator adapted toautomatically adjust the proportion of mixture according to a desiredrule, a fuel supplying pipe connecting said regulator with said sprayingnozzle, an atomizing air nozzle provided in said supplying pipe betweenthe regulator and the spraying nozzle, a throttle device comprising atleast one throttle slide provided at said air pipe and adapted to adjustthe output of the engine, an auxiliary venturi tube arranged coaxiallyto the main air flow and adapted to produce the rate of decrease of airpressure required for the regulation of atomizing air supply, the exitmouth of said auxiliary venturi tube being coincident with the narrowestplace of the throttle device.

2. Carburettor for internal combustion engines comprising, incombination, an air pipe having a venturi adapted to form the mixtureand to produce a vacuum for sucking-in the fuel, and a nozzle adapted tometer the rate of flow, a spraying nozzle provided at the throttle placeof said air pipe, a regulator adapted to automatical- 1y adjust theproportion of mixture according to a desired rule, a fuel supplying pipeconnecting said regulator with said spraying nozzle, an atomizing airnozzle provided in said supplying pipe between the regulator and thespraying nozzle, two throttle slides provided in the air pipe andadapted to adjust the output of the engine, means adapted to adjust saidslides, an auxiliary venturi tube the entrance opening of which isarranged on the axis of the said air pipe and the exit opening of whichis arranged on the middle axis of the throttle cross section formed bysaid throttle slides, the front faces of said slides being provided withsemi-cylindrical recesses adapted to enclose the exit mouth of theauxiliary venturi tube, when the slides are adjusted to the idle runningposition, and having Venturi-tube-like rounded and bevelled entrance andexit edges.

References Cited in the file of this patent UNITED STATES PATENTS

